Electrical connector, method and apparatus

ABSTRACT

An electrical connector formed by a die blanking operation having an improved smooth edge contact surface formed by a fine scraping of said edge to remove the rough fractured surface remaining after the blanking operation; also, the method and apparatus for forming said improved smooth contact surface.

United States Patent 1 1 Murray 1 1 Jan. 2, 1973 [541 ELECTRICALCONNECTOR, METHOD 3,248,686 "4/1966 Ruehlemann .339/47 R AND APPARATUS3,081,528 3/1963 Hanna ..339/258 R [75] Inventor: Ro ay y 3,354,85411/1967 Kosha ..ll3/119 151' b tht ,P.

e own a Primary Examiner-R1chardJ. Herbst [73] Assignee: AMPIncorporated, Harrisburg, Pa. Atmmey wmiam J (eating et aL [22] Filed:Aug. 28, 1970 211 Appl. No.: 68,033 [57] ABSTRACT An electricalconnector formed by a die blanking Related Applicafion Data operationhaving an improved smooth edge contact [62] Division of Ser. No.864,787, Oct. 8, 1969, Pat. No. surface formed by a fine scraping ofsaid edge to 3,587,502- remove the rough fractured surface remainingafter the blanking operation; also, the method and ap- [52] U.S.C1..113/119 51 1111. C1. .3210 53/36 2:2 formmg mpmved [58] Field ofSearch .1 13/1 19; 339/258 R, 242, 47 R,

339/95 R, 95 A, 95 T, 95 B, 95 D, 47 C; 72/39, 40, 340; 90/24 A; 29/630[56] References Cited 6 Claims, 15 Drawing F1gures UNITED STATES PATENTSPATENTEDJA 2191a SHEET 1 [IF 9 PATENTEDJAN 2191s w Mw PATENTEDJAN 2191asum 7 0F 9 3'707'932 ELECTRICAL CONNECTOR, METHOD AND APPARATUS This isa divisional application of application Ser. No. 864,787, filed Oct. 8,1969, now US. Pat. No. 3,587,502.

The present invention relates to electrical connectors having edgecontact surfaces and method and apparatus for making the same.

In the manufacture of-electrical connectors, particularly of thecrimp-type, most are blanked or stamped out on a progressive die from athin strip of flat metal stock. In some of these connectors the contactsurface (i.e., that surface of the connector which makes actualelectrical contact) is formed from the cross section of the flat metalstock. A problem has long existed in such edge contact surfaces whereonly a small portion of the cut edge forming the contact surface has asmooth shear. The remainder of this surface is formed by a break orfracture of the metal portion of the cut face.

This is apparently due to the methods required for accomplishing thesestamping operations. In a punch die it is typical that a spacing betweenthe punch and its corresponding die should be approximately percent ofthe width of the material being stamped out. Therefore, the piecestamped out on one side will take the shape of the punch and then willfracture outwardly (and downwardly) an amount approximately equal to thespacing between the punch and its die and then will shear the last 20 to30 percent of the cross section in a shape identical to the die.Typically, a piece thus blanked out will have an edge surface which is asmooth shear cut of about twenty percent and then is a rough fracturedundercut angled therebelow. It is possible to increase the percentage ofsmooth shear surface somewhat by a reduction in the clearance below the6 percent figure but only at severe penalties with relatively littlegain. Thus, by reducing this clearance and with liberal use ofspecialized lubricants one might be able to achieve 40 percent andoccasionally approach a fifty percent smooth shear surface but withgreatly increased power requirements, tool wear, and tool breakage andmany other detrimental trade offs well known to those skilled in theart. Since in the manufacture of more modern miniaturized connectorsthis fractured portion of these edge contact surfaces can amount to morethan eighty percent, the resulting design limitations and contactinefficiencies can be sufficient to render such connectors fatallyfaulty. In such connector design requirements the edge surface must havea minimum smooth shear surface of 50 percent consistently to beeffectively reliable. This problem becomes particularly acute whereeither the edge contact surface or the mating surface with which it isdesigned to make electrical contact has a cylindrical shape (circular orotherwise), because the contact area of such a connector becomes moredependent on-the' height of the contact surface and independent of itslength. The more brittle the material, the larger the break caused bythis fracturing.

Attempts to solve this foregoing problem by decreasing the punchclearance or by very fine shaving steps (i.e., subsequent fine stampingor blanking steps) did not meet with material success, since the degreblbreak was not materially reduced.

A second problem is encountered with the use of edge contact surfacesformed by stamping operations in a sliding contact which is to be madesubstantially perpendicular to the direction in which the surface was 5formed by stamping. This problem concerns the very small tool markswhich the stamping die leaves in the smooth" sheared contact surface butwhich are sufficiently large to act as a rasp-like surface which cansoon wear away the ultra-thin gold surface commonly used on matingcontact surfaces.

It is an object of the present invention to provide methods andapparatus for overcoming the problems discussed herein.

It is a further object of the present invention to improve theeffectiveness of edge contact surfaces of standard electricalconnectors.

It is yet another object of the present invention to provide electricalconnectors having edge contact surfaces which are substantiallyminiaturized and yet maintain superior contact qualities over similarprior connectors.

It is yet another object of the present invention to provide electricalconnectors having edge contact surfaces which give demonstrativelyincreased troublefree service.

It is yet another object of the present invention to provide method andapparatu s for producing such improved edge contact surfaces with onlyminor modifications or additions to current manufacturing methods andapparatus.

Broadly the methods and apparatus of the present invention achieve theseobjects by a scraping of the edge contact surface which results incutting away or planing the surface substantially along, rather thanacross, the surface. This scraping is done to a depth sufficient toremove substantially all evidence of the fracture and leave behind theexactly desired contour, typically flat, for said surface. This scrapingoperation is effective to remove thefractured surface without subsequentfracture, because it is done in a direction such that the metal is atall times substantially supported and does not cross an unsupportededge.

In this specification and the accompanying drawings I have shown anddescribed a preferred embodiment of my invention and have suggestedvarious alternatives and modifications thereof; but it is to beunderstood that these are not intended to be exhaustive and that manyother changes and modifications can be made within the scope of theinvention. These suggestions herein are selected and included forpurposes of illustration in order that others skilled in the art willmore fully understand the invention and the principles thereof and willthus be enabled to modify it and embody it in a variety of forms, eachas may be best suited to the conditions of a particular use.

In the drawings:

FIG. 1 is an isometric view of the stationary dies together withhold-down and'locating tools of the moving. die, illustrating a portionof a preferred embodiment of apparatus according to the presentinvention for forming improved edge contact surfaces (also showing thescraping and sizing device in the advance position on the stationarydie);

FIG. 2 is a plan view of the stationary die in FIG. 1 with the scrapingand sizing device shown in the retracted position, and additionallyshowing a strip of connectors in process);

FIG. 3 is similar to FIG. 2 but with the scraping and sizing device inthe advanced position and the holddown and locating tools also shown inposition as taken along lines 33 in FIG. 4',

FIG. 4 is a vertical cross-section through the moving and stationarydies when in engagement, taken along lines 44 in FIG. 3;

FIG. 5 is a vertical cross-section through the moving and stationarydies when in engagement, taken along lines 5-5 in FIG. 3;

FIG. 6A is an enlarged plan view partially in section of the sizingdevice;

FIG. 6B is a view similar to FIG. 6A showing the sizing device in theadvanced position and the hold-down and locating tools in plan section;

FIG. 7A is a greatly enlarged cross-section of a connector showing theedge contact surface after stamping;

FIG. 7B is similar to 7A but showing the edge contact surface afterscraping;

FIG. 8 is an enlarged detail in plan section of stamped connectors insuccessive stations after engagement of the two dies but prior toadvance of the scraping tool;

FIG. 9 is a view similar to FIG. 8 but showing the scraping tool in theadvanced position;

FIG. 10 is a view similar to FIG. 9 showing an alternative embodimentwith a double-edged scraping tool;

FIG. 11 shows a preferred embodiment similar to that illustrated inFIGS. 1-9 for producing a connector somewhat modified in shape from thatshown in the preceding figures being a plan view of the stationary diewith the scraping and sizing device in the retracted position and withthe sizing device and the adjustment for the backstop in partialsection;

FIG. 12 is a vertical cross-section taken along lines l212 in FIG. 11showing the two dies in engagement and particularly showing theadjustable backstop; and

FIG. 13 is similar to FIG. 12 but showing the two dies in spacedrelation.

For convenience in discussing and illustrating preferred embodiments ofthe present invention, the figures have been related to a crimp-typeelectrical connector 10 having a conventional F-crimp terminatingportion 12 with a dual tine contact engaging portion 14 extendingtherefrom. These tines 20 are designed to cooperate to electricallyengage and mechanically grip a contact post 15 inserted in the slotformed between the opposing contact surfaces 18. This connector 10 asillustrated in FIGS. 2 to 10 is shown in strip form (i.e., stillattached to thelocating strip 16). This is the form in which suchconnectors are typically supplied to the customer for later applicationby automatic applicating machines. As can be most clearly seen fromFIGS. 8 to 10, this particular connector 10 has an arcuate edge contactsurface 18 on the inside of each tine 20 and has a retaining notch 22for holding the connector 10 in a molded connector block (not shown)when in service. In contrast, the connector 10b shown in FIGS. 11 to 13is somewhat simplified having no retaining notch 22.

FIG. 2 shows a portion of the stationary bottom die 24 of theprogressive die with the locating strip 16 carrying newly formedconnectors 10 attached thereto at spaced intervals. These connectors 10move in a stepby-step progression from one station to the next in anintermittent advance from left to right as viewed in FIG. 2.

FIG. 7A shows the rough-cut contact edge surface 18 of the connectortine 20 as it appears after having been blanked out in the previousforming operations. As can be seen from FIG. 7A in materials typicallyused for this type of connector, having a medium hardness and ofrelatively small cross-section, the break or fracture surface 26 is veryrough and non-linear over as much as percent of the edge surface of. thetine 20. Such a fracture surface is typically undercut so that theentire extent of this surface 26 is lost to making electrical contactwith the contact post 15 (shown in dash-dot outline). Even if thefracture surface 26 were in line with the contact edge surface 18, itsroughness would provide only very poor contact because only the highestpoints of the roughness would be in engagement with the post 15.Furthermore, this roughness would also score the post 15 as it slidesacross it, destroying any plating (which typically is gold). Thedestruction of the plated surface can be very serious in affecting thequality and longevity of the contact assembly, particularly ininstallations where repeated disconnections are made (as in changingfrom one pre-programmed plug-in control to another).

FIGS. 8 and 9 show in detail the scraping method of the presentinvention being performed by apparatus according to the presentinvention (which latter is more generally shown in FIGS. 2 and 3). FIG.7B shows the contact edge surface 18 after the scraping processaccording to the present invention has been performed. It can be seenthat this process has scraped off a layer of material 28 (see FIG. 9)leaving a straight, effectively smooth, superior contact surfacethroughout the entire extent of the edge 18. Any minor tool marks leftby such scraping are parallel to the direction of sliding contact and,therefore, relatively inconsequential.

As viewed in FIGS. 2 and 3, the connectors 10 shown at the far left arenewly formed and have yet to be processed according to the presentinvention, while those at the far right have been both scraped andsized.

After a connector 10 has been advanced to a position just opposite thefirst scraping tool 30 it is precisely positioned by strip pilots 32passing through strip pilot holes 34 in the strip 16 and on into pilotholes 36 in the stationary die 24. Spring loaded strip holders 38 clampthe strip 16 in position. At the first scraping station, the right-handtine 20 of the connector 10 therein is supported from beneath by support40. Hold-down tool 42, carried on the upper moving die 44, firmlypositions the tine 20 on the support 40 preventing any twisting of thetine 20 but permitting a limited horizontal motion therebetween.Positioned between the two hold-down tools 42 are two flexible stops 46.These stops 46 move down with the upper die 44 and pass into slots 48made in the tine supports 40. These stops 46 engage the outer portionsof the tines 20 when the latter are held in position between thehold-down tools 42 and their respective supports 40. during the scrapingoperation. These stops 46 serve both to prevent the tine 20 from beingoverstressed and also to maintain a proper pressure of the tine 20against the scraping tools 30 or 50, see FIGS. 3, 5 and 8, andespecially FIG. 9 (which latter shows the flexibility of the stops 46).

It will be noted that the first six connectors from the left in FIGS. 2and 3 have their tines oriented in a slightly open V-orientation ratherthan substantially parallel as illustrated at the right in these samefigures. This was done in order to leave sufficient room between thetines on a given connector 10, to permit passage of the scraping toolsor 50 therebetween to gain access to the blanked out contact edgesurface 18'.

In order to shape the connector to its final design configuration, theymust pass through a sizing opera tion. In the connectors illustrated inFIGS. 1 to 10 this sizing operation is complicated by the shape of thetines 20 having a retaining notch 22. As during the scraping operation,the tines 20' of the connector 10 are firmly held to prevent twistingbut to permit horizontal displacement during the sizing operation. Thetines are supported from below by support 52 (see FIG. 4)' and are heldthere against by a hold-down tool 54. As can be seen from FIGS. 2 and 3,and FIGS. 6A and 68, as the movable sizing unit advances horizontallyperpendicular to the strip 16 to engage the tines 20 in the sizingstation, the sizing fingers 56 pass on either side of the tines 20(while the latter are gripped between the hold-down 54 and itscorresponding support 52). As the fingers 56 advance, their outer edges(beveled at 45) engage the sizing cams 58 (similarly angled). Furtheradvancement of the fingers 56 causes them to be squeezed togetheragainst the pressure of the spring 60 and about pivot 62 therebyengaging the spread tines 20 and forcing them inwardly into a parallelorientation.

As illustrated in this preferred embodiment, the transverse carriage 64used for advancing both the scraping tools 30 and 50 and the sizingfingers 56 are shaped to track in a horizontal transverse directionrelative to the progression of the strip 16 through the progressive die.This carriage 64 tracks in guide slots 66 and 68. It is actuated by aslide cam 70 which depends from the upper movable die 24. As the cam 70moves downwardly, it bears upon the cam follower pin 72 (which latter isfixed in the carriage 64) forcing the carriage 64 forward towards thelocating strip 16 and the connectors 10 carried thereon. The scrapingtools 30 and 50 are carried in front of the leading end of the carriage64 by a slide block 74 having a locating screw adjustment 76. The sizingfingers have a similar slide block 78 and screw adjustment 80.

FIG. 10 shows an alternative embodiment of the present invention whereina single scraping tool 30a has two scraping edges. For convenience ofreference, features similar to those illustrated in the precedingfigures have been given identical reference numerals followed by thesuffix a. e

As indicated above, FIGS. 11 to 13 indicate still another preferredembodiment of the present invention. Where the parts are equivalent tothose illustrated in FIGS. 1 to 9, identical reference numerals havebeen employed, and where they are substantially equivalent but ofdifferent structure, the same reference numerals have been employed butfollowed by the suffix b." The connectors 1012 have tines 20b which donot have retaining notches 22. Because of this, the sizing mechanism isgreatly simplified, being only a sizing cam 82 having a graduallytapered cam slot (as illustrated in FIG. 11) which has a height onlyslightly greater than the thickness of the tines 20b and has a tapershaped to force the ends of the tines 20b together into the designedconfiguration.

Also illustrated in FIGS. 11 to 13 is an improved version of the tinestops 46b (best shown in FIG. 13). The main advantage of the stopillustrated in FIGS. 11 to 13 over that illustrated in FIGS. 1 to 9 isits adjustability. This adjustability not only enables quick andconvenient compensation for tool wear and for differing pressurerequirements responsive to design variations, but also initially inachieving the proper design pressure. If the pressure which the tinestop 46b exerts against the tine 20b is too great, then the scrapingtool 50 will tend to gouge and chatter thus destroying rather thanimproving the contact surface.

The actual backstop portion of the adjustable tine stop 46b is a finger84 positioned to operate in the slots 48 made in the tine supports 40.This finger 84 is carried by a rigid arm 86 which is pivoted on pin 88carried in housing 90. In the illustrated embodiment the pin 88 servesas a pivot pin for both arms 86. The adjacent faces of the arms 86 atthe point of engagement of the pin 88 arecylindrically recessed toreceive the pin 88 therein and capture it therebetween with therespective adjacent faces spaced one from the other. The outer face ofthe free end 92 of the arm 86 is engaged by a spring loaded probe 94which is forced into engagement therewith by spring 96. The pressure ofthe spring 96 is adjustably varied by thumb screw 98. Once the desiredspring loading has been achieved; this adjustment can be maintained bythe set screw 100. As can best be seen in FIG. 13, the housing iscarried vertically by springs 102 which serve to raise the finger 84 outof engagement with the tines 20b thereby permitting advancement of theconnectors l0b on the locating strip 16b to the next station. Thehousing 90 is pressed down into operative position against springs 102by the spring loaded probe 104 which seats in socket 106. Thus, afterthe connector 10b has been positioned for scraping, the upper moving die44b moves downwardly carrying the probe 104 with it and forcing thehousing 90 and the finger 84 of its arm 86 into operative position asillustrated in FIG. 12.

With the tine stop 46b positioned as illustrated in FIG. 12, thepressure of the finger 84 against the tine 20b can be increased byscrewing the thumbscrew 98 inwardly. The adjustable spring tensionserves not only to increase the pressure exerted by the finger 84, butalso gives the finger 84 the flexible pressure required where thecontour of the tine edge contact surface 18b is curved.

Although it is mechanically possible and within the scope of the broaderaspects of this invention to make these backstops 64 rigid rather thanflexible and have the scraping tool move in a cammed path following thecontour of the tine edge contact, nevertheless this would beconsiderably less desirable because of the extremely precise positioningof the tine that would be required and the very close tolerances whichwould have to be maintained.

It has been found that for a particular material and contour of the tinethe scraping angles of the cutting tool can be surprisingly critical.For example, in the embodiment illustrated in FIGS. 1 to 9 when theleading face of the cutting edge of the scraping tools 30 was angled at30 to the perpendicular through the point of the tool and the trailingface was angled at 40, the tool tended to gouge the surface and did notfunction properly. Similarly, a 45 angle did not function properly.However, when these angles were modified to 43 (and used on a tine madeof number sixhardness phos bronz with a thickness of 0.016 inches), thisscraper advancing in a linear direction scraped off a curl 28 from thecurved contact surface 18' which had a thickness of 0.0005 inches. Thiswas enough to improve the smooth surface of the edge contact surfacefrom about 20 percent to over 60 percent. Anything over 50 percent whichcan be achieved with any regularity is a significant improvement greatlyincreasing the utility of the contact. Furthermore, other trialscrapings with this same arrangement resulted in consistent improvementof the edge contact surface to a consistent removal of 90 to 100percent. This scraping method is applicable to surfaces formed frommetals having a thickness up to at least 0.030 inches.

It is an advantage of the scraping method disclosed herein that thisprocessing can be accomplished within very minute and confined spacesand at a very high production rate (300 scrapings per minute beingtypical). In contrast, a rotary cutter or grinder would be comparativelybulky, slow and leave circular rather than linear tool marks. Thegrinding material would tend to become imbedded in the kind of metalstypically encountered in electrical contacts. In a typical applicationof the embodiment illustrated in FIGS. 1 to 9, the shank of the scrapingtool had a thickness of 0.020 inches and a height of 0.l60 inches withthe scraping point extending out from the shank at essentially rightangles by about 0.01 inches. For improved wear characteristics, thepoint of the tool could be formed on a diamond insert.

I claim:

1. In a method of making an edge engaging electrical connector having aneffectively flat edge contact surface wherein the connector is initiallyblanked out from flat metal stock with the blanking operation forming asubstantially rough and nonlinear cut edge surface which constitutes aninefficient contact surface for the connector, the improvement whichcomprises the step of:

fine scraping the cut edge by cutting away a thin metal layer from saidcut edge to remove at least a substantial portion of said rough andnonlinear cut edge surface and to produce a substantially neweffectively flat edge contact surface thereby increasing the area andquality of said edge contact surface of said connector.

2. In a method of making an edge engaging electrical connector having aneffectively flat edge contact surface as claimed in claim 1 wherein saidscraping is directed along said cut edge.

3. In a method of making an edge engaging electrical connector having aneffectively flat edge contact surface as claimed in claim 1 wherein saidscraping is performed substantially along the direction of contactengagement intended for said edge contact surface.

4. In a method of making an edge engaging electrical connector having aneffectively flat edge contact surface as claimed in claim 1 wherein saidscraping is performed by: I

maintaining an effective pressurized and yieldable engagement between astraight cutting edge of a scraping tool and said out edge of saidconnector; and

simultaneously moving said scraping tool relative to said connectoralong the direction of contact engagement intended for said edge contactsurface. 5. In a method of making an edge engaging electrical connectorhaving an effectively flat edge contact surface as claimed in claim 4wherein leading and trailing faces of the straight cutting edge of saidscraping tool are provided and maintained at a substantial angle to thedirection of contact engagement intended for said edge contact surface.

6. In a method of making an edge engaging electrical connector having aneffectively flat edge contact surface as claimed in claim 4 with saidedge contact surface having an ultimate clearance less than the size ofsaid scraping tool, the improvement further comprising the steps of:

initially blanking out said connector from the flat metal stock so thatsaid cut edge of said connector has a clearance sufficient toaccommodate said tool; and

sizing said connector to position said substantially new effectivelyflat edge contact surface at its ultimate clearance after theperformance of the fine scraping step. i

1. In a method of making an edge engaging electrical connector having aneffectively flat edge contact surface wherein the connector is initiallyblanked out from flat metal stock with the blanking operation forming asubstantially rough and nonlinear cut edge surface which constitutes aninefficient contact surface for the connector, the improvement whichcomprises the step of: fine scraping the cut edge by cutting away a thinmetal layer from said cut edge to remove at least a substantial portionof said rough and nonlinear cut edge surface and to produce asubstantially new effectively flat edge contact surface therebyincreasing the area and quality of said edge contact surface of saidconnector.
 2. In a method of making an edge engaging electricalconnector having an effectively Flat edge contact surface as claimed inclaim 1 wherein said scraping is directed along said cut edge.
 3. In amethod of making an edge engaging electrical connector having aneffectively flat edge contact surface as claimed in claim 1 wherein saidscraping is performed substantially along the direction of contactengagement intended for said edge contact surface.
 4. In a method ofmaking an edge engaging electrical connector having an effectively flatedge contact surface as claimed in claim 1 wherein said scraping isperformed by: maintaining an effective pressurized and yieldableengagement between a straight cutting edge of a scraping tool and saidcut edge of said connector; and simultaneously moving said scraping toolrelative to said connector along the direction of contact engagementintended for said edge contact surface.
 5. In a method of making an edgeengaging electrical connector having an effectively flat edge contactsurface as claimed in claim 4 wherein leading and trailing faces of thestraight cutting edge of said scraping tool are provided and maintainedat a substantial angle to the direction of contact engagement intendedfor said edge contact surface.
 6. In a method of making an edge engagingelectrical connector having an effectively flat edge contact surface asclaimed in claim 4 with said edge contact surface having an ultimateclearance less than the size of said scraping tool, the improvementfurther comprising the steps of: initially blanking out said connectorfrom the flat metal stock so that said cut edge of said connector has aclearance sufficient to accommodate said tool; and sizing said connectorto position said substantially new effectively flat edge contact surfaceat its ultimate clearance after the performance of the fine scrapingstep.